1. Field of the Invention
This invention relates to air handling equipment and more particularly to a centrifugal blower assembly.
2. Description of the Prior Art
In the field of air handling equipment, centrifugal blower assemblies have long been employed for uses such as ventilation, fume exhaust, material handling, and the like. Blower assemblies have been designed in almost every conceivable size, volumetric output capacity and pressure range. Also, these blowers have been constructed in down-draft, side-draft, up-draft, and various other angular configurations. However, regardless of the application and the above described variables, centrifugal blower assemblies are all provided with the same basic components and operate in the same basic manner.
In general, the prior art centrifugal blower assemblies comprise a spiral-shaped housing normally fabricated of sheet metal and welded into a one piece structure. The housing is provided with an air inlet opening formed in at least one of the spaced side walls, and a centrifugal outlet through which exhaust air is expelled. An air moving rotor or impeller is positioned within the housing along the axis of the air inlet openings. The rotor is demountably carried on an axle shaft and is rotatably movable therewith. The ends of the axle shaft extend laterally from opposite ends of the hub of the rotor and are journaled for rotation in bearings carried centrally within the air inlet openings by suitable braces.
Driving of the rotor is usually accomplished by a suitable drive means, such as an electric motor, which is directly coupled to the axle shaft either by a gear drive assembly or a pulley belt arrangement. An alternate method of driving the rotor is to provide a belt driven pulley on the periphery of the rotor. Such a drive system is fully disclosed in U.S. Pat. No. 3,702,741, issued on Nov. 14, 1972 to the same inventor.
Optimum air handling characteristics dictate that the diameter of the air inlet openings in the centrifugal blower housing be less than the diameter of the rotor. Due to this and the one piece construction of the housing, it will be seen that installation and removal of the rotor can only be accomplished through the centrifugal outlet of the blower housing, and such movements cannot be accomplished with the axle shaft assembled thereto due to the laterally extending ends thereof. Thus, the length of the axle shaft necessitates that it be removed or installed by axially sliding it through one of the air inlet openings.
Thus, with the centrifugal outlet being the only opening in the blower housing that is large enough for the rotor to pass through, it will be seen that servicing problems will result in many instances. To illustrate that problem, consider that in almost every instance, installation of a centrifugal blower assembly is accomplished by supportingly positioning the assembly adjacent a horizontal or vertical structure, such as the roof or wall of a building, and connecting the centrifugal outlet to the building's duct work. To install or remove a rotor from a blower assembly mounted in that fashion requires that the entire assembly be removed from the supporting structure and from the ducts to which it is connected in order to gain access to the centrifugal outlet.
This problem of access is more serious in centrifugal blower assemblies of the type in which the rotor is peripherally driven, i.e., a drive belt engages a pulley disposed on the periphery of the rotor. The simple act of changing a belt or other servicing of such assemblies is extremely difficult due to the air inlet openings being smaller than the periphery of the rotor.
One solution to the above discussed problems relating to access is fully disclosed in U.S. Pat. No. 3,746,464, issued to the same inventor on July 17, 1973. In the structure disclosed in that patent, the spiral-shaped portion of the blower housing is formed with a removable segment which, when removed, provides an access opening into the interior of the housing for servicing purposes and through which the rotor can be passed. This particular structure however, cannot be employed in all instances to solve the access problem. For example, when the centrifugal blower assembly is mounted within a conventional evaporative cooler housing, the cooler housing itself is often disposed proximate the spiral-shaped portion of the blower housing in such close relationship that removal of the removable segment cannot be accomplished.
Other problems exist with regard to centrifugal blower assemblies; namely, the cost of fabrication and the corrosive environment in which such assemblies oftentimes operate.
Since the rotor of a centrifugal blower is a rotating structure, such factors as rotor balance, precision alignment of the rotor hub, axle and bearings and rotor support braces are critical. If those factors of balance and alignment are imperfectly achieved the result will be an inefficient and noisy assembly. Therefore, fabrication of a quiet and efficient centrifugal blower assembly is a relatively costly project.
The cost of such assemblies is further aggrevated when the centrifugal blower is to be employed in a corrosive environment such as in an evaporative cooler. In such instances, the axle, rotor, hubs, bearing and the like must be fabricated of materials which retard corrosion, and an efficient lubrication system must be employed.
Therefore, a need exists for a new and useful centrifugal blower assembly which overcomes some of the problems of the prior art.